Advances in genetically encoded sensor and effector proteins have introduced unprecedented opportunities for the study of complex biological processes in vivo that provide an opportunity to rapidly advance knowledge critical to the understanding and treatment of cardiovascular and cardiopulmonary diseases. These optical tools have not been widely exploited due to the lack of available transgenic mouse lines expressing these reagents in relevant tissues. Such genetic reagents could be easily and efficiently deployed for the study of NHLBI relevant biology and disease, transforming the capacity of NHLBI scientists. We propose the creation of purpose -designed mouse lines that express Ca2+ sensors and Optogenetic cell activators in NHLBI relevant tissues. The Genetic Resource for Optical Signaling will consist of 50 mouse lines designed for combinatorial crosses enabling the co-expression of sensors and effectors, or red and green Ca2+ sensors in interacting lineages. This strategy will enable the combination of two synergistic technologies (Ca2+ sensors and optogenetic proteins) through simple, high-yield crosses that constrain expression of the transgene to cells of interest. As such, the resource will enable NHLBI researchers to conduct experiments not otherwise possible in a cost effective and highly efficient manner, accelerating the use of optical genetic tools and markedly accelerating scientific discovery. The Genetic Resource for Optical Signaling (GROS) will create and validate the lines, communicate their availability, and permanently bank them for distribution to the scientific community following the funding period. RELEVANCE: We will create a resource that advances cardiovascular and cardiopulmonary science consisting of lines of mice expressing 3rd generation optical sensors and cell activators in lineages of relevance to NHLBI science. These mice will be fully characterized and made available to the community, creating permanently available reagents that will markedly enhance the capabilities of hundreds of scientists. (End of Abstract)